The recipients have the right without further restrictions for each copy they receive, but the workaround is that if that right is exercised, grsecurity will never send them anything again. Thus, if one values the patchset, which their customers who are paying real money presumably do, they'll refrain from exercising their right to redistribute in order to stay off the blacklist.
That is not a "work around". That is a BLATANT in-writing VIOLATION of the no-restrictions-on-redistribution clause GRSecurity MUST follow in-order to have the PERMISSION to create derivative works.
GRSecurity IS violating the copyrights of the linux copyright holders upon whom it's derivative work is derived from.
